Furnace with multiple heat recovery systems

Abstract

In a furnace such as a glassmelting furnace, a portion of the combustion products formed by combustion of fuel with gaseous oxidant within the furnace are passed through a recuperative or regenerative heat exchanger system to heat a portion of the incoming gaseous oxidant, and a portion of the combustion products are passed instead through a secondary heat exchanger system, wherein the hot combustion products and oxidant which are passed through said first heat exchanger are passed at a heat capacity rate ratio of combustion products to oxidant of less than 1.3.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the energy efficient production of glass in a furnace, and more particularly to the method of heat recovery from hot combustion products formed in the combustion that is carried out to generate heat for melting glassmaking material.BACKGROUND OF THE INVENTION[0002]Many industrial operations employ furnaces within which fuel and oxidant are combusted so that the heat of combustion can heat material that is in the furnace. Examples include furnaces that heat solid material to melt it, such as glassmelting furnaces. Other examples include furnaces that heat solid material or objects such as steel slabs, to raise the material's temperature (short of melting it) to facilitate shaping or other treatment of the material or object. The challenges that furnaces present are illustrated in glassmelting furnaces, and much of the description herein of the present invention is described with reference to glassmelting furnaces, but the p...

AI Technical Summary

Benefits of technology

[0028]providing one or more controllable dampers that can alter the volumes of said combustion products that are fed to said primary heat exchanger system and to said secondary heat exchanger system.

Problems solved by technology

Even in glassmaking equipment that achieves a relatively high efficiency of heat transfer from the combustion to the glassmaking materials to be melted, the combustion products that exit the melting vessel typically have a temperature well in excess of 2000° F., typically in a range of 2600 to 2950 F, and thus represent a considerable waste of energy that is generated in the glassmaking operations unless that heat energy can be at least partially recovered from the combustion products.

However, the maximum achievable temperature and pressure of steam is limited by the relatively low temperature of the waste flue gas stream after a regenerator or a recuperator.

This maximum temperature is imposed by considerations of the capability of the materials from which the heat exchanger is constructed to withstand higher temperatures, and considerations of the tendency of the glassmaking material to begin to soften and become adherent (or “sticky”) if it becomes too hot during the heat exchange step, leading to reduced throughput and even plugging of the heat exchanger passages.

Because of the relatively low temperature of flue gas, however, the maximum preheat temperatures achieved by this method was limited to about 600° F. In addition the physical size of the commercially available batch / cullet preheater is very large in order to exchange heat with the large volume of flue gas, making it economically unattractive.

However, reducing the temperature of this stream of combustion products by adding to it a gaseous diluent such as air, and / or spraying a cooling liquid such as water into the stream, is disadvantageous as such approaches reduce the amount of recoverable heat remaining in the gaseous combustion products, increase the size of the gas handling equipment that is needed, and adds additional equipment and process expense.

However, the radiative batch / cullet preheater was hitherto considered not applicable for air fired regenerative or recuperative furnaces.

Images